This invention relates to a central dictation system and, in particular, to the generation and detection of various function commands and to the manner in which such functions are controlled in response to such commands.
Central dictation systems are known wherein a central record/playback unit is adapted to be individually accessed by any one of a plurality of remote dictate stations so as to record dictated information on a record medium. In such systems, the central record/playback unit can be accessed by only a single dictate station at any given time. While one dictate station is in communication with the central unit all other dictate stations are excluded, or locked out, from also communicating with the central unit.
The advantage of such central dictation systems is that individual dictators need not be concerned with the manipulation of various recording media, nor need they attend to the time consuming task of delivering recording media having dictation thereon to appropriate personnel for transcription. In the typical central dictation system, a recording medium having a relatively large capacity for recording dictation is provided so that received dictation communicated from a remote dictation system is recorded on the medium and can be subsequently reproduced for transcription. In one type of central record/playback unit, the record medium consists of an endless loop of magnetic tape which is driven past a dictation transducing station and is also driven past a transcribing transducing station. These stations are essentially operated independently of each other so that a dictation operation can be performed simultaneously with and independently of a transcribing operation. Thus, such a central dictation system advantageously permits the efficient use of dictating and transcribing apparatus. Moreover, dictated information can be almost immediately transcribed. A typical prior art central dictation system having an endless loop of magnetic tape is described in U.S. Pat. No. 3,817,436, issued June 18, 1974, and is assigned to Dictaphone Corporation, the assignee of the present invention.
Central dictation systems of the aforenoted type can be readily adapted to accomodate a high volume of dictation by providing plural record/playback units at a central location and by providing suitable switching apparatus which permits any one remote dictate station to gain access to any one of the plural record/playback units. However, it has been found that, as more central units are provided to thereby accommodate more remote dictate stations, the distance between many such remote stations and the central units becomes quite large. Consequently, it is necessary to provide conducting cables having extremely long length between such remote stations and the central units to permit information to be transmitted therebetween. The inherent resistance of very long conducting cables tends to deleteriously affect the levels of control commands which must be transmitted from the remote station to the central unit to control a dictation operation. Typically, such control commands have been represented by DC voltages of predetermined magnitudes or several magnitudes of resistances connected to the transmission path, each magnitude representing a control function, or command to be performed at the central unit. Unfortunately, the impedance loading effect attributed to the conducting cables distorts the control command magnitudes so that an erroneous command can be received at the central unit thus causing an improper function to be performed.
Although it is technically feasible to account for such loading effects prior to the installation of the central dictation system, it usually is impractical to adjust each remote dictate station function generator in accordance with the length of conducting cable extending betwteen that station and the central unit. In addition, for those applications wherein a remote dictate station can gain access to any one of plural record/playback units, and wherein such record/playback units are disposed at various locations, the resultant variations in cable length from the remote station to each central unit cannot be readily accounted for. Also, where the remote stations are connected through a switching apparatus, such as a conventional telephone PBX apparatus, various random cable lengths can be provided between the remote station and the record/playback unit ultimately connected thereto.
Therefore, it is one feature of the present invention to provide a control function generator in each remote dictate station that transmits function commands to the central units which are substantially unaffected by the cable length extending therebetween.
In central dictation systems of the aforenoted type, it often is necessary for a dictator to be furnished with the immediate transcription of dictated information. However, since a large amount of dictated information previously recorded on the endless magnetic tape might be awaiting transcription, a delay can be expected until such dictated information is transcribed. Although some central dictation systems permit a transcribing station to be switched from connection with the transcription head to the dictation head so as to effectively by-pass the stored tape awaiting transcription, and to thus immediately transcribe the dictated information last recorded on the tape, it has been found that this mode of operation is accompanied by various disadvantages. For example, if the dictation transducer of the record/playback unit is being used to perform a transcription operation, then that unit cannot be utilized to record dictation until such transcription operation is completed. Also, whereas the record/playback unit, when used in its normal modes of operation, advantageously permits the simultaneous recording of dictation and transcription of recorded dictation, the use of the dictation transducer for a transcription operation requires that the dictated information first be completed. The simultaneous dictation and transcription operation cannot be performed.
Therefore, it is another feature of the present invention to transfer a remote dictate station to a predetermined, additional record/playback unit so that dictated information having a high priority of importance can be transcribed almost immediately, and wherein simultaneous dictation and transcription operations can be performed.